The sugars important to the dietitian are glucose, cane or beet sugar, and maple sugar. Glucose is manufactured from corn by a conversion of the starch to sugar. This sugar made from corn differs from cane sugar in its simpler chemical composition, its formula being C6H42O6. While glucose is wholesome and cheap, it has not gained popular favor to any great extent, because it has a noticeably less sweetening power than cane sugar; because of its cheapness it .has been extensively used in cheaper grades of candy and cheaper table syrups, and sometimes resorted to as an adulterant to cane sugar, maple sugar, maple syrup, and honey. The glucose syrups are extensively used as table syrups, and while they are wholesome and cheap, they lack the pleasing flavor of maple syrup and of cane syrup.

Cane sugar or beet sugar, the common granulated sugar of the market, has two general sources, the sugar cane of the South and the sugar beet of the North. Sugar made from these materials possesses the formula C12H22O11, and is known to the chemist as saccharose. The brown sugars of the market usually represent saccharose in early stages of refining. These brown sugars and syrups, made from cane and beet sap, have a distinctive and rather pleasing flavor, which is naturally lost in the processes of refining, the pure granulated sugar being practically flavorless and possessing simply sweetness.

Maple sugar and maple syrup are produced from the sap of the sugar maple and the rock maple. These sugar-producing maples are found in the Northern States from Michigan and Indiana to the Atlantic, as well as in southern Canada. The trees are tapped in the early spring when the sap begins to flow; the sap is boiled down to syrup, or to the point of granulation in sugar, in a way very similar to the making of syrup and the brown sugars from cane or beet sap. Maple sugar possesses a flavor peculiar to itself and one which is very pleasing to most people. If the brown maple sugar were subjected to the refining processes it would yield a white, flavorless sugar almost identical to cane sugar, but the loss of its pleasing flavor would be too great a price to pay for refining, so we find maple sugar always marketed in the brown cakes. Being much higher in price, there is a great temptation to adulterate the maple sugar and syrup, and it is likely that many brands on the market have been thus adulterated. As they are, however, adulterated with saccharose, glucose, or a mixture of the two, the product is both wholesome and sweet, though it is likely to possess the distinctive flavor in a smaller degree because of the adulteration.

Sugars are easily soluble in water and require very little digestion to be ready for absorption. The glucose requires no digestion at all, and is ready for absorption as soon as it is dissolved in the saliva. The saccharose, however, requires to be split up or converted into its two component monosaccharid molecules (dextrose and levulose). This splitting of the saccharose into dextrose and levulose takes place in the small intestine, and is brought about by the influence of the ferment called invertin.

"While the sugars above mentioned are the only ones to which the dietitians need give any thought in the preparation of menus, there are other sugars which possess some importance as nutrients, and may be mentioned here. Milk sugar has already been mentioned as one of the constituents of milk. The sugar of milk is called lactose. This sugar is closely related to saccharose, having the formula C12H22O11. Like saccharose, it is a disaccharid, and requires to be split up into its monosaccharid molecules before it is absorbed. This splitting takes place in the small intestine under the influence of a ferment called lactose. The two monosaccharid sugars into which it is split are called dextrose and galactose.

Many of the vegetables and most of the fruits have sugar in smaller or larger quantities. The sweet potato, for example, owes its sweet taste to sugar, as is also the case with the beet, the carrot, the parsnip, the turnip, among vegetables; while among the fruits, the sweet taste, wherever found, is due to the presence of sugar. Grapes possess large quantities of sugar, so also do plums, cherries, figs, and dates. Most fruits possess sugar as practically their sole nutrient, the other parts of the fruit being simply a cellulose pulp, water and mineral salts in solution, together with a flavor peculiar to each particular fruit. The sugar of fruits and vegetables is in most cases a reducing sugar, usually either dextrose (C6H42O6) or fructose (C6H42O6).

/ Sugars are the most easily assimilated fuel foods, and are capable of oxidation within a few minutes after they have been taken into the stomach. For this reason they have been used by athletes, by mountain climbers, and soldiers in their feats of strength and their forced marches, because a few lumps of sugar taken with two glasses of water will begin to yield energy in the form of heat and muscular strength within, at most, thirty minutes after they have been taken. While sugars may be thus used in emergencies, they possess two rather positive disadvantages - namely, the tendency to surfeit the appetite, so that one after a short time would take his ration at first without relish, then later with positive disgust. Another disadvantage with sugar as a ration is the readiness with which it can be thrown into a state of fermentation in the stomach. As we shall learn in a subsequent chapter, the presence of sugar in the stomach is not followed by a secretion of the gastric juice. Whenever the quantity of gastric juice is below the normal during the period of digestion, the chance for fermentation is greatly increased, as the acid of the gastric juice tends to stop sugar fermentation.

Notwithstanding these two disadvantages of sugar as a special ration, (we can hardly emphasize too strongly the great advantage of sugar as a moderate and reasonable part of a regular mixed diet. The greater the muscular activity of the individual, and the lower the temperature to which he is subjected, the greater the need for this particular foodstuff. Men who are doing heavy work out of doors in the winter time can take prodigious quantities of sugar, syrup, and molasses with only favorable results. As a rule, men working under such conditions crave sweets, and their craving may be taken as a natural indication that they need sweets.